The present invention is directed to a motor-driven compressor comprises a drive shaft driven by an electric actuator and acting on a crank mechanism having a crank to which a connecting rod is eccentrically connected and the connecting rod is connected to a piston movable in a corresponding cylinder.
With particular reference to the field of refrigerators, a motor-driven compressor used in a domestic appliance of this type has a cylinder in which the respective piston moves, and which has a longitudinal axis generally perpendicular to the axis of the drive shaft. The latter is generally perpendicular to a surface supporting the refrigerator. The axis of the cylinder, in particular, lies in a plane containing the longitudinal axis of the connecting rod at each point of the stroke of the piston in the cylinder, the plane being parallel to that in which the crank lies.
This solution consequently involves a fairly large vertical dimension of the motor-driven compressor. As a result of this and in order not to have very hulky motor-driven compressors, the dimensions of the cylinder have to be kept within limited values. It is therefore impossible to increase the displacement of the motor-driven compressor beyond certain values, clearly involving problems which also adversely affect the flowrate per unit time of the coolant fluid circulating in the refrigerator circuit.
Moreover, known solutions require the various parts of the crank mechanism and the drive shaft to be formed with considerable precision in order to achieve the required perpendicularity between the longitudinal axis of the cylinder and the drive shaft. This is to prevent any jamming of the piston in the cylinder and of the connecting rod on the eccentric pin, which would clearly involve problems in the use of the compressor.